<template>
  <div>
      =={{msg}}
     <input  type="button" @click="say()" value="btn"/>
  </div>
</template>

<script>
import {reactive} from  'vue'
/* 目的：setup中直接定义的数据  不是响应式数据   reactive函数 */
export default {
  setup () {
    var msg='hello  vue3'
    const say = () => {
      console.log(msg)
      msg='修改后的msg'
    }
    return {msg,say}
  }
}
</script>

<style lang="scss" scoped>

</style>